Mississippi Democratic U.S. Senate candidate Travis Childers today became the first Democrat to sign an anti-amnesty pledge from the Federation for American Immigration Reform (FAIR), a unexpected and extraordinary play that could significantly change the dynamics of his campaign against incumbent Sen. Thad Cochran (R-MS).

Childers, a former Congressman, signed the pledge Thursday that was seized on by Cochran’s Republican primary challenger, state senator Chris McDaniels, to draw a contrast with Cochran on the issue of immigration. The pledge includes language about amnesty but is also against increases in legal immigration.

The primary race, one of the most bitterly fought contests in recent memory, has left deep wounds in Mississippi, and some conservative activists said Childers’ choice to sign the pledge could sway them to vote for the Democratic candidate.

“It looks to me like Mississippi voters have a choice,” Kevin Broughton, a Mississippian and spokesman for a national grassroots conservative organization, told Breitbart News. “One candidate is on the record opposing amnesty for illegal aliens; has never voted ‘no’ on building a fence on the Southern border; and has never, to my knowledge, played the race card against conservatives. The other is Thad Cochran.”

Cochran won the primary after his allies used polarizing racial appeals to Democratic voters to sway them to vote in the GOP primary. Without Democratic votes, experts have said, Cochran would have lost the race.

Childers embrace of the pledge could give him a coalition of Democratic voters and disenchanted conservatives.

“The Barbours had a cynical, two-part plan from June 3 – June 24,” Broughton said. “One: Shower Democrat voters with food stamps and plead for votes, to engage in vicious race-smears using Bennie Thompson-type tactics. It will be interesting to see if that works against a Democrat in the general.”

The last public poll of the Cochran-Childers matchup was conducted in late August, showing Cochran with a 15 point lead.

During the primary, McDaniel, who is still pursuing a legal challenge of the primary election results, made waves nationally by becoming the first–and arguably at the time the highest profile political figure nationally–to take the FAIR pledge.

FAIR’s pledge includes three planks. The first is to oppose “any form of work authorization” for illegal aliens. The second is to oppose legislation that would increase the number of legal immigrants. The third is to oppose bills that increase the number of “guest workers.”

“What we’ve seen over the past several years is a combination of wage stagnation, growth in welfare programs and even shrinking workforce participation,” McDaniel said in an interview with Breitbart News when he signed the pledge. “That comes in large part because of out of control illegal immigration but also because of increased numbers of legal immigration. We have millions of Americans who don’t have a job, plus we have millions who are on public benefits. How about we find a way to put those people back to work?”

At the time, and since then, Cochran has declined to sign the pledge. One of Cochran’s biggest backers, former Mississippi Gov. Haley Barbour, is one of the most powerful backers in the national Republican Party of amnesty for illegal aliens.

The Mississippi GOP primary between McDaniel and Cochran was one of the bloodiest intra-party battles in recent history, and resulted in calls for RNC chairman Reince Priebus to remove Henry Barbour–Haley’s nephew and the head of the Super PAC “Mississippi Conservatives” that was behind much of the anti-Tea Party attack ads. Priebus has not responded publicly to the calls.

Childers signing the pledge could lead to a whole number of scenarios that national Republicans haven’t dealt with or thought of before. If Childers pulls off an upset win, and assuming he caucuses with Democrats if elected, Republicans would need to pick up an extra seat to win the majority in November. There would also likely be a push for him to caucus with Republicans, adding additional drama.

This move also has massive implications in the Democratic Party. By and large, over recent years, the Democrats have moved toward supporting a full-scale open borders type immigration policy. But Democrats just a decade or so ago didn’t always feel that way–liberals like Barbara Jordan, a Houston-area congresswoman, and red state Democrats regularly opposed amnesty and open borders type policies. If Childers is successful in pulling this off–meaning he either makes this into an aggressively competitive race, or wins–it could have a wide-reaching effect on Democrats as well, meaning they may no longer support as lock-step a belief on immigration as the party’s liberal leaders currently push. Other Democratic candidates nationwide may soon embrace what Childers is doing too, and it’s not that far of a stretch to perhaps see some red state or southern Democrats back the play.